Relay



Aug. 18, 1936. o. D. GRANDSTAFF RELAY Filed April 26, 1935 INVENTOR.

OTHO D. GRANDSTAFF ATTORNEY.

Patented Aug. 18, 1936 UNITED STATES PATENT OFFICE RELAY Otho D. Grandstaff, Chicago, Ill., assignor, by

mesne assignments, to Associated Electric Laboratories, Inc., Chicago, 111., a corporation of Delaware Application April 26, 1935, Serial No. 18,288

13 Claims.

acter, which is economical to manufacture .and

adapted to a wide range of commercial applications.

The construction of the new relay will be explained hereinafter in connection with the accompanying drawing, in which Fig. 1 is a top view of the relay; Fig. 2 is a side view; while Fig. 3 is a view of the bottom of the relay, or a view of the relay rotated from the position in which it is shown in Fig. 1.

Referring to the drawing, the various parts of the relay are all mounted on an L-shaped base or base plate 2. The leg 30 of the base plate is provided with tapped holes such as 3I, whereby the relay may be mounted on an ordinary relay rack by means of screws. The plate 2 is preferably of brass or other non-magnetic metal.

On the lower side or bottom of the base plate 2 are two permanent magnets 3 and 4. As shown clearly in Fig. 3, these magnets are secured against the base plate 2 by means of two clamping members 5 and 6, and four screws 1, 8, 9, and I0. These clamps and screws also should be of nonmagnetic metal. The magnets are arranged with unlike poles together, as shown. The size of the air gaps can be regulated by slightly loosening the screws I-IU and then tapping the magnets into the exact position required. It will be noted that no pole pieces are used and that the magnetic circuit is continuous except for the air gaps between the opposed ends of the magnets.

On the upper side of the base plate 2 there is a coil I I, and associated parts, which will now be explained. The coil II is wound on a spool 34, which is secured to base plate 2 by means of two brackets I2 and I3 and screws such as I4. There is an opening extending axially through the spool 34 to accommodate the core I5. The opening is just slightly larger than the core I5, so that the core is free to rotate. The core I5 is provided with armatures I6 and IT, and is supported on two steel reeds I8 and I9, which in turn are clamped to the base plate 2. Explaining the core and armature construction more in detail, the core I5, and likewise armatures I6 and I1, is preferably made of iron of high magnetic permeability. The core I5 is slotted at opposite ends to receive the reeds I8 and I9. Each armature comprises a slightly tapered portion of rectangular cross section reaching down into the associated air gap and a cylindrical portion having an opening of the correct size to make a tight fit when the armature is forced onto the core I5. The core I5 and the armatures and supporting reeds are assembled with the coil II before the latter is mounted on the base plate 2. opening in spool 34, and then the reeds I8 and I 9 are placed in the slots in the core. The ends of the core may be slightly tapered, so that the armatures I6 and I! can be started on. By means of a press the armatures are then forced on to 0 the core into the position shown in Fig. 2. Thus the core, armatures, and reeds are securely held together.

After assembling the coil and associated parts,

the spool 34 of the coil may be mounted on the 15 9 base plate 2 as previously mentioned. The base plate 2 is provided with openings 35 and 36, so that the armatures I6 and I! can pass through the base plate into the air gap between the magnets. The reeds I8 and I9 may then be secured in place.

Considering the means for securing reed I8, there is a brass block 20 secured to the base plate 2 by means of a pair of screws such as 32. This block has a semi-cylindrical recess or slot in its upper face. 2|, which has a similar recess or slot in its lower face. When the two blocks are assembled as shown the two slots correspond and form a cylindrical opening in which are positioned two semicylindrical members 26 and 21, one on each side of reed I8. Block 2| is secured to block 20 by means of four screws such as 31. It will be clear that by assembling the parts as explained and by then tightening up the screws 31 the reed I8 will be firmly held.

The reed I 9 is clamped between members 24'and 25 by means of blocks 22 and 23 in a similar manner.

The armature I 6 is just long enough to pass through the corresponding air gap. Armature I1, 40

such as 49. The leg 4| of bracket 40 stands per- 50 pendicular to base plate 2, as seen in Fig. 2. The various springs, insulators, etc., are clamped together and to the upright leg 4|, by means of screws 54; These screws are threaded in member 4I, whereby part of the assembly is clamped 55 The core I5 is placed within the Above block 20 there is a block 25 between H and the heads of the screws, and extend beyond member ll far enough to enable the remainder of the assembly to be clamped between member GE and the nuts 55.

Considering this assembly more in detail, the terminal 52 is not insulated on the upper side and provides for connecting with the armature ll which is the movable contact member. The circuit extends from terminal 32 by way of screws 5 2, bracket it, base plate 2, block 2'2, and reed l8 to armature ill. In other words, the movable contact member and terminal 32 are on the frame. The contact springs between which the movable contact member or armature ll operates are denoted by 45 and 36. These springs have a slight tension away from ll, which causes their ends to bear against adjusting springs 56 and El, respectively. Springs 56 and El also are tensioned away from ll, but are held in the proper position by adjusting screws 53 and 52, respectively. The latter are threaded in the comparatively stiff spring members 55 and 5t and are provided with lock nuts as shown.

The coil H may have any desired number of windings depending on how the relay is to be used. A very useful arrangement is to provide two windings which can be connected either in series or in parallel. One winding may be connected to terminals it and M and the other to terminals M and 48. 6E] and iii are two bushed holes in base plate 2 through which conductors from the windings of coil l i may be led to the terminals.

The utility of a polarized relay is well known. In describing the operation of the present relay, therefore, it will be assumed for the sake of simplicity that it is connected to a source of alternating current, with the two windings of the relay in series. The alternating current source is connected to terminals 53 and 48, and terminals A l and ill are connected together.

With the current ofi, the armatures l6 and H may stand at the center of their respective air gaps. When the current is turned on, the core I5 is magnetized and the relay responds. Assuming that when first turned on the direction of current is such that armature l6 becomes the north pole and armature H the south pole, both armatures will be attracted by magnet 3 and repelled by magnet l. Therefore the core it will be rotated Within coil M and armature ll will make contact with spring The rotation takes place against the resistance of the reeds l8 and it), which offer an increasing force opposing the movement. This opposing force, however, increases with a straight line characteristic, while the magnetic force depends on the square of the distance between the magnet 3 and the armatures. As this distance decreases by rotation of the core the magnetic pull will build up somewhat faster than the opposing spring pressure and armature ll will engage spring as with good contact pressure. The adjustment of the air gaps is such that the rotation of the core i5 is stopped by engagement of armature ill with spring 45 before the arma tures H and It reach the poles of magnet 3.

New at this stage of the operation a considerable portion of the flux produced by magnet 3 will be diverted by the armatures through core Hi. This flux will tend to hold the core in rotated position asthe current in the coil decreases, but is opposed by the reeds i8 and it which tend to restore the armatures to mid position. The point at Which the armatures begin to restore depends on-whether the relay is adjusted for stay put operation or not. By this expression is meant an adjustment such that the armatures will be held in either position by the pull of the adjacent permanent magnet alone and without current in the coil. For rapid response to alternating current such adjustment is not desirable, and in the present case therefore the adjustment will be such that some time before the current in the coil reaches zero the pressure stored in the tensioned reeds will over power the pull of the magnet 3 and the restoration of the armatures will begin.

After falling to zero the current in the coil will start to build up in the opposite direction, thereby reversing the polarity of the core l5 and causing armature it to become the south pole and armature ill the north pole. Both armatures are accordingly attracted toward magnet l, causing armature ii to engage spring 35. On the assumption that the relay has a symmetrical adjustment the operation on this side will be the same as described.

Adjustment of the relay for various operating requirements will now be explained. For the maximum sensitivity the permanent magnets should be adjusted so that the air gaps are as short as they can be without permitting the armatures to strike the poles of the magnets. The sensitivity is a function of the pull exerted by the permanent magnets. By shortening the air gaps the pull of the magnets is increased and therefore the sensitivity also. The design of the relay permits very powerful permanent magnets to be used and hence great sensitivity can be secured.

If high sensitivity is to be retained and at the same time a very rapid response is desired, as would be the case if the relay is to be used to respond to weak alternating currents of a frequency of perhaps 60 cycles or higher, a considerable part of the pull of the permanent magnets must be balanced out by the reeds l8 and I5. These reeds can be made stiiier by decreasing their efiective length, which is done by moving the clamping members 25, 2'5, 24, and 25 toward the core l5. Increasing the stiffness of the reeds does not affect the sensitivity, because the opposition to rotation produced by the reeds is zero at mid point of the armatures no matter how stiff the reeds are. But it will be clear that increased stifiness of the reeds does speed up the response of the relay because it causes the armatures to start to restore sooner on a falling current in the coil.

The extent to which the foregoing adjustment can be carried out depends on the contact pressure required. This will be obvious because the contact between ll and 65 or it is made by the magnetic pull against the resistance offered by the reeds. For maximum rapidity of response in any given case, the proper procedure is to calculate the minimum allowable contact pressure and the minimum operating current that will be avail able, and then adjust the reeds as stiffas they can be and still secure the necessary contact pressure with the minimum operating current.

It will be appreciated that great rapidity of response can also be secured by adjusting the magnets so as to increase the length of the air gaps, leaving the reeds with an average adjustment. This method of adjustment, however, will secure increased speed of response at the expense of a somewhat decreased sensitivity.

For certain uses it is necessary that the relay have a stay put adjustment, which means, as previously explained, that the armatures will stay in either operated position upon cessation of current in the operating coil. This adjustment is made by shortening the air gap or decreasing the stiffness of the reeds, or both, until the desired operating characteristic is secured. The relay can be biased in only one direction if desired by an unsymmetrical adjustment of the magnets. Thus if magnet 3 is moved up close while magnet 4 is moved away somewhat, the relay can be made to stay put with contact 45 closed but not with 46 closed.

Pointing out some of the advantages of the relay, it will be clear that the relative simplicity of the design, which involves among other things the use of only a single coil, makes it a very economical relay to manufacture.

The arrangement of the magnetic circuit with armatures operating in two air gaps is very efficient. By using powerful magnets and balancing out part of the magnetic pull with torsional springs great sensitivity and rapidity of response can be secured.

The elimination of pole pieces avoids a common source of loss in other relays where such pole pieces are employed. There is always an increased reluctance in the magnetic circuit if pole pieces are employed due to impossibility of making a perfect connection between the pole pieces and the magnets.

The use of a single coil and the spaced relation of this coil to the magnetic structure greatly reduces the losses which ordinarily arise from leakage flux. Consideration of the several views of the drawing will show that the coil is well removed from the magnets, due to being in a different plane and because of the spacing between the magnets, which makes all portions of the turns on the coil highly effective in producing fiux in the core I5.

As mentioned before the core I5 is just slightly smaller than the bore of the spool 34 in which it rotates freely without touching. Consequently air damping such as is caused by drawing in and expelling air is eliminated. This is a decided advantage over those constructions which employ a vibratory armature positioned in the bore of a coil or coils. A further advantage over such constructions lies in the fact that the opening through the coil need only be enough larger than the core I5 to provide for free rotation, and does not have to afford space for lateral displacement. The average distance of the coil turns from the core may therefore be decreased adding to the eificiency. The spool 34, for instance, may comprise a thin walled fiber tube with the heads as shown, which brings the inner turns of the coil very close to the core.

Other advantages lie in the adaptability of the relay to different uses and the facility with which its adjustments may be changed to alter its operating characteristics, together with miscellaneous features of improvement which lend desirability to a device of this character.

The invention having been described, that which is believed to be new and for which protection of Letters Patent is desired will be pointed out in the appended claims.

What is claimed is:

1. In a polar relay, a magnetic circuit including two air gaps, a fixed coil, a core supported for rotation in said coil, and armatures extending from the opposite ends of said core into said air gaps.

2. In a polar relay, a magnetic circuit including two air gaps, a fixed coil, a core supported for rotation in said coil, an armature on one end of said core extending into one of said air gaps, an armature on the other end of said core extending through the other air gap, and contacts adapted to be operated by the end of said last mentioned armature. 5

3. In a polar relay, an operating coil, a core within said coil, means including two reeds supporting said core for rotation within the coil, an armature attached to said core, and a magnet adjacent said armature adapted to move the same and rotate the core against the tension of said reeds when the coil is energized.

4. In a polar relay, a magnetic circuit including two air gaps, a coil, a core loosely fitting in said coil, means including two reeds for supporting said core for rotation, armatures extending from opposite ends of said core into said air gaps, whereby said armatures will be operated upon energization of the said coil, and means for adjusting the stiffness of said reeds so that upon deenergization of the coil the said armatures will be retained in operated position or not depending on the operating characteristic desired.

5. In a polar relay, the combination with a spool comprising a thin walled tube and heads on opposite ends thereof, a winding on said spool, a core of magnetic material having a diameter slightly smaller than the bore of said tube, means supporting said core for rotation within said spool, and means including a magnet and an armature on said core for rotating the same responsive to energization of said winding.

6. A core and armature assembly for a polar relay comprising a rod of magnetic material, said rod being slotted at both ends, two reeds, one inserted in each slot, and two armatures also of magnetic material, said armatures having openings therein and being forced on to the slotted ends of said core tosecure the reeds in position.

7. In a polar relay, a magnetic circuit including two air gaps, an armature positioned in one air gap, contacts adapted to be operated by said armature, a second armature positioned in the other air gap, means for magnetizing said armatures, whereby said first armature operates said contacts, and means including a mechanical connection between said armatures whereby the second armature when magnetized delivers power to said first armature to assist the same in operating said contacts.

8. In a polar relay, a rotatable shaft, a magnetic circuit including an air gap, a coil surrounding said shaft for magnetizing the same, electrical contacts, a lever arm attached to one end of said shaft for actuating said contacts, and an armature attached to the other end of said shaft and extending into said air gap, said armature responsive to the magnetization of said shaft to rotate the same and apply power to said lever arm.

9. In a polar relay, a base plate, a permanent 60 magnet mounted on one side of said plate, a coil mounted on the other side of said plate, a rotatable core for said coil, openings in said plate opposite the ends of said core, and armatures extending from the ends of said core through said openings and into operative relation with the poles of said magnet.

10. In a polar relay, a magnetic circuit including a permanent magnet and an air gap, a coil, a core extending axially through said coil, means 7 supporting said core for rotation on the coil axis, means for rotating said core comprising an armature attached to the core outside said coil and extending within said air gap, and an electrical contact operated responsive to rotation of said core.

11. In a polar relay, a magnetic circuit including a permanent magnet and an air gap, a coil, a rotatable core extending through said coil and having its rotation axis coincident with the axis of the coil, an armature for rotating said core, said armature comprising a crank having one end attached to said core and the other end extending within said air gap, and resilient means arranged to oppose rotation of said core.

12. In a polar relay, a magnetic circuit including a permanent magnet and an air gap, a coil, a rotatable core of which a portion lies inside said coil, the axis of the core coinciding with the axis of the coil, means for rotating said core comprising a crank-like armature attached to the core and extending within said air gap, and resilient means normally maintaining said armature at a predetermined position in said air gap and ofieranon ma ing an increasing resistance to rotation of said core in either direction.

13; In a polar relay, two permanent magnets, means supporting said. magnets with the poles of one magnet adjacent the unlike poles of the other magnet but spaced away therefrom, thereby forming a magnetic circuit which includes the two magnets in series and two air gaps, a rodlike core supported for rotation, armatures for rotating said core, said armatures extending from spaced points on the core into said air gaps, a coil on said core between said armatures, means supporting said coil in a fixed position where its axis coincides with the axis of said core, and electrical contacts operated responsive to rotation of said 15 core OTHO D. GRANDSI'AFF. 

